Descriptions

Permanent magnet synchronous machines (PMSMs) are widely used in electric vehicles and hybrid electric vehicles to propel the wheels. Various control strategies have been developed for PMSM drive systems to achieve both high efficiency and safe operation. In a PMSM drive system, generally the high voltage battery and the power converters are connected by a relay. In vehicle key-off events, although the battery is isolated immediately from the relay, the DC bus filter capacitor has to be discharged as quickly as possible to avoid an electrical hazard. This research explores the DC bus capacitor discharge of PMSM drive systems for hybrid/electric vehicles. Based on analyzing the power flow during discharge, a three-stage discharge algorithm has been developed, including a fast discharge stage, a DC bus voltage closed-loop regulation stage, and an inverter shutdown stage. The DC bus capacitor is quickly and safely discharged by dynamically adjusting the command currents for the current vector control of PMSMs. Both simulation and experimental results show the feasibility and performance of the proposed discharge technique.